The present invention relates to an ossicle prosthesis that replaces or bridges at least one component or parts of a component of the ossicular chain.
The ossicle prosthesis includes, at one end, a first fastening element designed as a top plate for mechanical connection with the tympanic membrane and, at the other end, a second fastening element for mechanical connection with a component or parts of a component of the ossicular chain or with the inner ear; it also includes a connecting element that connects these two fastening elements in a sound-conducting manner. The top plate includes a radially outer annular region, a radially inner—central, in particular—attachment region for mechanically attaching the top plate to the connecting element, and several segment elements for radially connecting the radially outer annular region with the central attachment region. A device of this type is made known in DE 20 2005 003 782 U1.
Ossicle prostheses are used in cases in which the ossicles of the human middle ear are missing or damaged, either entirely or partially, to conduct sound from the tympanic membrane to the inner ear. The ossicle prosthesis has two ends. Depending on the specific circumstances, one end of the ossicle prosthesis is fastened to the tympanic membrane, e.g., using a top plate, and the other end of the ossicle prosthesis is fastened, e.g., to the stapes of the human ossicular chain, or it is inserted directly into the inner ear. In many cases, with the known ossicle prostheses, sound conduction between the tympanic membrane and the inner ear is limited, because these known ossicle prostheses do not fully replace the natural anatomical formations of the ossicular chain.
After the prosthesis has been surgically implanted in the middle ear and the tympanic membrane has been closed, the recovery phase begins. Scars form during this period, and they produce unforeseeable forces, which can cause the prosthesis to move out of its localized position. When there is a stiff connection between the top plate and the shank, increased pressure peaks can result between the edge of the top plate and the tympanic membrane, or the graft between the tympanic membrane and the top plate. These pressure peaks can be so high that penetration or extrusion through the tympanic membrane would result. For this reason, it is very helpful for the prosthesis to have a certain amount of post-surgical mobility, so that the top plate can automatically adapt, post-operatively, to the position of the tympanic membrane.
Since, in addition, the unique anatomical features of the ear, such as the position, shape and size of the stapes, incus, hammer and tympanic membrane vary, it is very advantageous when ossicle prostheses are not designed to be rigid, but rather that they have a certain amount of flexibility or variability.
To attain this level of flexibility/variability, it is known to use various fastening and attachment devices for ossicles that have elastic parts and/or joints. A hinged connection of this type between a fastening element which can be installed on the base of stapes and the longitudinal shank is described in EP 1 181 907 B1, and is offered by the applicant under the trade mark “Ball-Joint”.
A further complication that occasionally arises is caused by inadequate ventilation of the middle ear space and the associated inflammation, tumor formation, adhesions in the region of the tympanic membrane, and stiffening thereof. When the eustachian tube malfunctions, for example, under pressure may form in the middle ear, which can cause the tympanic membrane to protrude (or retract), thereby resulting in adhesion, e.g., with the stapes. To counteract this, and to enable post-operative motions of the tympanic membrane to be emulated, the top plates of known ossicle prostheses are designed to be tiltable relative to the connecting element that connects the top plate with the second fastening element and is usually designed as a longitudinal shank. A top plate of this type, which is rigid yet tiltable relative to the connecting element is described, e.g., in US 2004/0162614 A1I, in the article M. W. YUNG, Ph.D., F.R.C.S., D.L.O., C. BREWIS, F.R.C.S., “A comparison of the user-friendliness of hydroxyapatite and titanium ossicular prostheses”, The Journal of Laryngology & Otology, February 2002, Vol. 116, pp. 97-102, or, e.g., in US 2006/0271190 A1.
The disadvantage of these known ossicle prostheses, however, is that, due to the rigid tilting of the top plate that occurs when the tympanic membrane performs localized medial motions, the opposite side of the top plate is moved laterally outwardly, thereby resulting in pressure peaks on the tympanic membrane.